Focusing problems with the fresnel groundglass on the Chamonix 45N-1?

[joshdaskew]

Hi, I recently bought a Chamonix 45N-1 and have to say it really is a lovely camera.. At the same time, I have bought a Schneider Xenotar 135mm 3.5 and plan to shoot portraits with this lens wide open. At some point I will buy a 150mm 2.8 ( although I have found focusing trickier enough with this lens ). After doing some tests with this camera I noticed that the focusing was way out and was pulling a foot or so in front of what was focused on the groundglass ( after receiving film back ). I borrowed my friends Linhof to test with the same lens and sure enough, on getting the film back, what I focused on was in focus. I contacted Hugo who in turn contacted the Chamonix factory and they told me that this was the first in the factories history to have this problem and that the the problem was related to the fact that I was using a lens like the Xenotar wide open and that the groundglass that comes installed as a default on the Chamonix is a fresnel and this is apparently known for having issues with fine focusing. So I sent my back off to China and they have sent me two groundglasses back, the original fresnel and a non fresnel ( to be used with these faster lenses wide open ). Has anyone ever come across such a problem or able to shed some light on it? I haven't had a chance to test this yet but I hope the problem is fixed by the new groundglass.. Any information anyone could provide would be fantastic. Thanks. Best regards Stefan

P.S Have used my friends account as I don't have one yet.

[Brian Ellis]

Some fine focusing difficulty is inherent in any Fresnel lens. One of the reasons people pay $250 and up for Maxwell screens is that they're the easiest Fresnels to focus, at least the easiest I've used and I've used most of them. That's also one of the reasons some people prefer a plain ground glass. However, it isn't normal to be a foot off. Is this your first LF camera or your first with a Fresnel screen? If so, my guess is you just weren't used to the Fresnel and so weren't focusing it properly (what kind of screen does your friend's Linhof have?). But it's hard to say much more until you've tested your new viewing screens. It's conceivable that you got a Fresnel lens that wasn't properly matched to the focal length of the lens you were using (e.g. they inadvertantly put a wide angle Fresnel on your camera and you weren't using a wide angle lens) but this doesn't seem too likely. You were using a loupe and a dark cloth, right? FWIW, the screen on my Chamonix was fine.

As an aside, you probably know that the widest aperture on many LF lenses is there mainly to assist in focusing. It isn't generally expected that it will be used to make photographs so you likely aren't going to get the best quality images using a 3.5 or 2.8 LF lens wide open.

[mandoman7]

The main concern is that the position of the film in the holder replicates the position of the ground glass surface when inserted, so the film is in the exact position of the surface that's used for focussing. This is something that should be checked with any newly acquired lf camera (micrometer). I've regretted shooting a lot of film and founding out afterwards about a discrepancy.

In my experience, fresnels often get weird out towards the edges with wide angles, but the center is usually pretty usable for focussing. I've never heard of a fresnel focussing differently with certain lenses. In this case, having more than one lens would help with diagnosis, as well as broadening the learning curve.

[joshdaskew]

Hi, Thanks for the responses, much appreciated! I will write back more when I have done some actual tests with the new groundglass but that won't be till early next week. Brian in response to your answer, I used to have a Linhof Technika 5 but I never used it with this lens. With the original fresnel groundglass on the Chamonix, I did a couple of tests. One comparison was to shoot with the Xenotar @ 3.5 and a Rodenstock Sironar - N I have @ 5.6. Both images came back with focus falling ahead of what I had originally focused on. Both images appear sharp on the ground glass and it is only when I got the film back that you can see the results. To be honest, I don't think it was that my focusing was out. When I compared it with my friends Linhof
( which I think is a non fresnel screen ) the object was spot on in focus when the film came back.

So as I said, will post some more when I have tested out the non fresnel variety with the Chamonix. Will be interesting......

As for shooting wide open, the look I am after is to have an extremely sharp drop of focus for portraits and this is the only way to achieve this.... How much of a degradation of quality are we talking here? I mean it is still 5 x 4 inch film right, so the quality has to be somewhat decent I would have thought?

As for the Maxwell screen, I have heard this recommended by a few people. Is this something that I would have to find to adjust or would I have to send him my camera for him to do. At this stage I am a little sick of sending my camera all over the world...

To Mandoman7, I am definitely aware of how important a ground glass screen is to be spot on with the film plane of your double dark slide, what is the best way to test this? I am not particularly technical.....

Ok, thanks again so much for your responses... Will post some more early next week. Best regards Stefan

[joshdaskew]

So after receiving a new back to my Chamonix 45N-1 with a non fresnel screen ( which I thought was fantastic customer service by the way - Thanks Hugo ) I have done some more tests with my Xenotar 135mm @ 3.5 and they have come back in focus with the non fresnel and out of focus with the fresnel type. Is this really just a case of me not being able to use the fresnel type properly? I mean, I intend to use this for portraits, so focus has to be spot on.. Any thoughts? Thanks to everyone who answered before. Cheers Stefan

[pocketfulladoubles]

As for the Maxwell screen, I have heard this recommended by a few people. Is this something that I would have to find to adjust or would I have to send him my camera for him to do.

This is a great question. Has someone tried a Maxwell screen on the Chamonix yet, and if so, how did it fare with the 90mm lens focusing issue? Did you need to shim it or make any adjustments to calibrate the focal plane?


Edit: Oh well, neuroticism got the best of me so I broke down and just ordered the Maxwell Ultra Brilliant screen. I'm also likely sending it in to have the focal plane calibrated. I'll let you know how it goes.

[Mark Jaremko]

This answers a lot of my questions, I've had a very frustrating month with this problem. My Chamonix 45N arrived in May, and most of my photographs are very much out of focus. I shoot mainly landscapes, so am focusing on infinity, but am also shooting them at night, so need the faster apertures, or else I'm standing for 45 minutes to take a single photograph. I know they're in focus on the GG, this I can see quite clearly through my loop, but so far only shots at F16 are beginning to approach being in focus.

One additional problem I've noticed is that the film plane and GG/Fresnel plane are not parallel. I have about 20 sheets, all shot with various lenses, various new film holders, and at various apertures and all of them show the image more in focus on the far right side and less in focus on the far left side. This consistency seems to indicates a problem worse than just Chamonix not compensating for the Fresnel thickness in placing the GG. Given that I seem to be the third person in a few weeks to notice this, has anyone else seen this?

I do trust that Chamonix will help resolve this (I only emailed Hugo about this today), but folks have mentioned about sending their cameras in to be "calibrated". Who does this sort of calibration?

[NewBearings]

Mark,

Try placing the fresnel on the external GG surface and using critical focus wide open with the same night scenes, but in daylight. Use a loupe to see if the focus plane is flat on the gg. Also check to see if your film carriers are sitting flat on all four edges when in the camera.

What lenses have you used when having focus trouble?

I did have a similar (uneven) problem with some images with my 90mm Rodenstock with the fresnel between lens and GG. I'm still running tests, so too soon to tell about flatness of film back.

[Paul Droluk]

One additional problem I've noticed is that the film plane and GG/Fresnel plane are not parallel. I have about 20 sheets, all shot with various lenses, various new film holders, and at various apertures and all of them show the image more in focus on the far right side and less in focus on the far left side. This consistency seems to indicates a problem worse than just Chamonix not compensating for the Fresnel thickness in placing the GG. Given that I seem to be the third person in a few weeks to notice this, has anyone else seen this?

I only recently acquired my first wooden field camera, a Chamonix 5x8. I've always used metal cameras, like the Toyo 45AII, but wanted to get a feel for what the wooden camera experience is all about. While the Chamonix does seem decently made (I haven't put a micrometer to it) I'm really amazed by the total lack of "0" detents. It means you have to zero every aspect of the camera via GG inspection, for each and every new shot! While I'm very much into the slow-down mantra of LF shooting, having to go through this tedium for each new set up is a bit over the top... IMHO.

[pocketfulladoubles]

I do trust that Chamonix will help resolve this (I only emailed Hugo about this today), but folks have mentioned about sending their cameras in to be "calibrated". Who does this sort of calibration?

Bill Maxwell referred me to Bill Moretz of Pro Camera, Inc. The screen is going straight to him for installation.